Radiological Physics and Technology

Early-age Ndufs4 knockout mice are an inappropriate animal model of Leigh syndrome

Early detection of elevated lactate levels in a mitochondrial disease model using chemical exchange saturation transfer (CEST) and magnetic resonance spectroscopy (MRS) with 7T MR imaging

Proposal of a new method to prove that unnecessary information is not drawn on the image using statistical analysis Abstract The purpose of this study is to propose a new method of image evaluation using statistical analysis. We used the Sign test and the Wilcoxon test to analyze the statistical significance of image differences. Using this method, we evaluated whether the small electrode of the DAP meter appears in the X-ray image. Two observed values, which were obtained by averaging all values under all exposure conditions, were compared. All the observation tests showed the same sign. Thus, the results proved that the small electrode of the DAP meter is not present on the image. Using this method, it became possible to prove that the electrode was not depicted, which was impossible to determine using conventional methods. The method combining both the Sign test and the Wilcoxon test can be useful in image evaluation.

Development of a new image manipulation system based on detection of electroencephalogram signals from the operator's brain: a feasibility study Abstract Physicians require an adequate display system with a console within arm's reach to view images during surgical operations and interventional radiological examinations. However, manipulation of the console by physicians themselves may not be possible because their hands may be otherwise engaged. In this study, an image manipulation system using an electroencephalogram (EEG) sensor mounted on the operator's head was developed. In this system, data acquired by the device is used to manipulate images, and the output can be converted to commands for various actions such as paging, which can be controlled by the operator's eye-blink, and zooming of a region indicated by the cursor, which can be controlled by the operator's mental concentration. In this study, the MindWave Mobile headset was used as EEG sensor, and AZEWIN for the display system. Ten observers were enrolled and fitted with EEG device to determine the threshold values of blink strength and attention; threshold value of 100 for blink strength and 65 for attention were determined. Thirty-one observers were enrolled and fitted with EEG device to investigate average response-time; the average response time for detecting paging was 0.43 ± 0.02 s, and that for zooming was 5.85 ± 0.56 s. Thus, the proposed image manipulation system using the operator's EEG signals enabled physicians to assess and manipulate images without using their hands.

Voxel-based morphometry analysis of double inversion-recovery magnetic resonance imaging for detecting microscopic lesions: a simulation study Abstract Double inversion-recovery (DIR) imaging has the potential to improve the detection of subcortical lesions through the use of voxel-based morphometry (VBM) analysis. The aim of this study was to clarify the characteristics of detectable lesions by performing a VBM analysis on DIR images of simulated lesions. Twenty healthy volunteers underwent magnetic resonance imaging using a head three-dimensional DIR sequence. The images were processed using SPM12; then, the selected images with simulated lesions were analyzed via VBM. The VBM results were evaluated using free-response receiver-operating characteristic curves and a receiver-operating characteristic analysis. The sensitivity was 100% (5/5), with 5.6 false-positive objects per case, in simulated lesions with a contrast of 0.6 and a size of 2.4 mm. The sensitivity was 80% (4/5), with 5.4 false-positive objects per case, in simulated lesions with a contrast of 0.5 and a size of 2.4 mm. The mean area under the curve value was increased from 0.783 to 0.883 using VBM, with a statistically significant difference (p < 0.01). The VBM analysis of the DIR images using SPM alone showed the potential to detect subcortical microscopic lesions. Early detection of Alzheimer's disease may be possible by adapting VBM in the clinical setting.

Estimation and validation of the frequency responses of a scanner system and an image reconstruction system in X-ray computed tomography Abstract In computed tomography, factors that theoretically affect the modulation transfer function (MTF) in the region near the isocenter are the frequency responses of the scanner system (MTFS) and reconstruction processing (MTFA). Although MTFS and MTFA are performance indices that are not disclosed to the users, both can be estimated by the measured MTF with the use of theoretical formulas. In this study, we proposed two methods to obtain the MTFS and MTFA, and confirm their validity. The first method to obtain the MTFS and MTFA uses a theoretical formula and the measured MTF. Another method uses the measured MTF and the noise power spectrum. In both the methods, the MTFS and MTFA were obtained separately. By our proposed methods, performance indices that are not usually disclosed to the users can be known.

Appropriate echo time selection for quantitative susceptibility mapping Abstract The purpose of our study was to clarify the dependence of quantitative susceptibility mapping (QSM) on echo time (TE). We constructed a phantom consisting of six tubes; three tubes were filled with different concentrations (0.5, 1.0, and 2.5 mM) of gadopentetate dimeglumine (Gd-DTPA), and three were filled with different concentrations (100, 200, and 350 mg/mL) of calcium hydroxyapatite. Real and imaginary images from multi-echo spoiled gradient-echo data (12 echoes) were acquired. We then used four datasets with three serial echoes. The QSM procedure consists of four steps: field map estimation, phase unwrapping, background removal, and dipole inversion. For each sample, we compared the measured mean susceptibility value with the theoretical susceptibility value and conducted a linear regression analysis. Accordingly, the relationship between the measured susceptibility and concentration of Gd-DTPA was shown to agree well with the theoretical values (TEs = 16.4, 20.8, and 25.2 ms; slope = 0.24, R2 = 1.00). Furthermore, the relationship between the measured susceptibility and concentration of hydroxyapatite also showed good linearity (TEs = 16.4, 20.8, and 25.2 ms; slope = − 0.00121, R2 = 1.00). In conclusion, the optimization of the TE in QSM makes it possible to obtain more detailed information regarding the susceptibility of biomaterials.

Clinical application of biological fingerprints extracted from averaged chest radiographs and template-matching technique for preventing left–right flipping mistakes in chest radiography Abstract We aimed to evaluate the identification performance achieved using biological fingerprints extracted from averaged chest radiographs and template-matching techniques for the prevention of left–right flipping mistakes. We produced averaged chest radiographs for each sex by averaging 100 posteroanterior chest radiographs. Further, 400 and 566 chest radiographs were used in consistency and validation tests, respectively, and they were flipped horizontally to produce flipped chest radiographs under the assumption that the left–right flipping mistake occurred. The correlation values obtained with chest radiographs and those obtained with flipped chest radiographs were calculated. When we used correlation indices calculated from the correlation values from four biological fingerprints except for the lung apex, 96.5% (386/400) and 95.8% (542/566) of the left or right sides were identified correctly in the consistency and validation tests, respectively. This result indicates that our proposed method would be promising for the prevention of left–right flipping mistakes.

A new approach for detecting abnormalities in mammograms using a computer-aided windowing system based on Otsu's method Abstract Breast cancer is the most common cancer and the leading cause of cancer deaths in women worldwide. This study aimed to provide an automatic windowing method in mammograms, based on the principles of Otsu's thresholding function, to help radiologists more easily detect abnormalities on mammograms. A total of 322 mammographic images from the Mammographic Image Analysis Society (MIAS) database were used in the present study. The image background was removed based on Otsu's method. After selecting the threshold in the computer-aided windowing (CAW) system, the pixel values were kept larger than the threshold and displayed on a grayscale. A radiologist evaluated images randomly before and after CAW. Using CAW, the radiologist correctly diagnosed all healthy images (207 images). A total of 115 mammograms were evaluated to differentiate malignancy from benign masses. All 63 benign images were accurately diagnosed after using CAW. Moreover, of 52 malignant images, all were accurately recognized as malignant except one, which was recognized as benign. Therefore, specificity and sensitivity were significantly improved to 98% and 99.6%, respectively, and the area under the receiver operating characteristic (ROC) curve was calculated to be 0.99. The study showed that the use of CAW can potentially lead to quicker image assessment and improve the diagnostic accuracy of radiologists in differentiating between benign and malignant masses on mammograms.

Comparison of volumetric-modulated arc therapy and intensity-modulated radiation therapy prostate cancer plans accounting for cold spots Abstract This study compared dosimetric indices of volumetric-modulated arc therapy (VMAT) with intensity-modulated radiation therapy (IMRT) accounting for cold spots in prostate cancer plans. IMRT plans were retrospectively generated from 30 prostate cancer patients with ten cases for each risk group, who received VMAT plans. The mean, maximum, and minimum doses, and conformity and homogeneity indexes were evaluated for planning target volume (PTV) and the mean dose and V20–V70 for organs at risk (OAR) including the rectum, bladder, right and left femoral heads, and rectum overlapped with PTV (ROP) regions. The numbers and volume percentages of cold spots within PTVs and ROP regions were measured using in-house software. Three-dimensional probabilistic distributions of the probability and distributions of cold spots were generated using a centroid matching technique for visualization and analysis. There was a statistically better dose conformity in the PTV, rectum, and bladder dose-sparing in VMAT compared to that in the IMRT plans, whereas VMAT had statistically worse target dose homogeneity, and right and left femoral head dose-sparing than those of the IMRT plans. The average volume percentage of cold spots per PTV for the VMAT was 4.37 ± 2.68%, which was smaller than the 5.72 ± 1.84% observed for IMRT plans (P = 0.007). The volume percentage of cold spots per ROP for the VMAT did not significantly differ from those for the IMRT plans. Compared with IMRT, the VMAT plans achieved better PTV dose conformity, OAR dose-sparing, and smaller cold spots in the treatment of prostate cancer.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
Crete.Greece.72100
2841026182

6948891480

alsfakia@gmail.com